The present invention relates to a testing apparatus of a magnetic recording medium or a magnetic head, for testing the magnetic recording medium or the magnetic head, which are able in write-in and read-out.
Conventionally, in information processing apparatuses, such as a work station, etc., magnetic recording apparatuses have been used as an outer recording apparatus thereof. It is well-known that, in particular, magnetic disc devices are developed, due to improvement on magnetic substance or on a magnetic head and also due to progress on signal processing technology, in high density of recording and high frequency of recording, as well as in lowering of the price thereof, in recent years, and it bears a burden of high speed and price-lowering of the information processing apparatuses.
Also, the magnetic disc apparatuses are required to be high in the reliability on data being recorded/reproduced, as the outer recording apparatuses, then for testing the magnetic disc or the magnetic head which is applied into a magnetic disc apparatus, a method is often used, in which the testing is carried out by recording/reproducing the test data with use of the magnetic disc or the magnetic head, at the frequency being used in actual practice.
In particular, with the magnetic disc, evaluation and testing are carried out on the disc as an object to be tested, by recording/reproducing the test data which is recorded on the magnetic disc, for example by performing a parametric test, wherein is measured TAA (Track Average Amplitude) as an average amplitude of a disc reproducing signal, such as shown in FIG. 11, as a test parameter recommended by the International Disc Drive Equipment and Materials Association (IDEMA), or PW50 as an average pulse width of the disc reproducing signal at a point of 50% of the average amplitude (TAA).
Also, the evaluation and testing are carried out on the disc as the object to be tested, by performing a certify test, wherein is detected a missing error, in which the amplitude of the disc reproducing signal is reproduced at a unit of data pulse and with an amplitude being too much smaller than the averaged amplitude of the disc reproducing signal when conducting the write-in/read-out of constant frequency data onto the magnetic disc, or a spike error, in which it is reproduced with the amplitude being too much larger than the average amplitude, etc.
FIG. 10 is a drawing for showing the structure of a testing apparatus of the magnetic recording medium or the magnetic head, according to the conventional art.
In the testing apparatus shown in the FIG. 10, first a magnetic disc 101 as the object to be tested is operated to rotate by a disc rotation portion 103, on the contrary to this, a test signal St of frequency fo is generated in a test signal generator circuit 602, so as to be added to a write-in controller circuit 603, wherein a test data is produced in the write-in controller circuit 603, being converted into a write-in current at a certain level in a write-in/read-out amplifier 601, and is written one by one onto the magnetic disc 101 through a R/W head 102 which was acknowledged to be a good-qualified one or was known in the magnetic characteristics thereof.
After completing the write-in, from the track on the magnetic disc 101 onto which the test data is written, the disc reproduction signal is reproduced by the R/W head 102 through the read-in/write-out amplifier 601 as two (2) signals of a positive phase and a negative phase, to be sent to an amplifier (AMP) 604 for level adjusting. Those two (2) disc reproducing signals Ss1 and Ss2 (each being a signal of frequency fo and corresponding to the test signal St), being adjusted in the level there, are inputted into a TAA detection circuit 605, a PW detection circuit 605 and a wave-form comparator circuit 608.
The TAA detection circuit 605 is constructed with using, for example, a voltage comparator circuit (comparator), a controlled current source, a capacitor and a one-turn track integrator circuit (not shown in the figure), wherein the voltage for charging the capacitor and the voltage of the disc reproducing wave-form are compared with, so that an envelope voltage in vicinity of a peak value of the disc reproducing signal is detected while controlling the controlled current source by means of the comparator, so as to charge the capacitor when the voltage of the disc reproducing wave-form is higher than the voltage for charging the capacitor, thereby detecting an integrated value of the envelope voltage for the period of one-turn or one-round of the track by means of the one-turn track integrator circuit.
Conducting dividing process upon the integrated value of the envelope voltage by the time for one-turn of the track, namely by treating averaging process onto the envelope voltage of the disc reproducing signal, the average amplitude value TAA of the disc reproducing signal is detected, so as to be outputted to a slice level producing circuit 606.
Also, a CPU 111 of a controller portion 110 reads the average amplitude value TAA, being the output of the TAA detection circuit, so as to perform measurement of TAA.
In the slice level producing circuit 606, the voltage of 50% with respect to the voltage level of the TAA is set to be a threshold value (i.e., a slice level), as a slice setting 1, to provide an output into a PW detector circuit 607, while, by means of a control signal P outputted by the CPU 111 of the controller portion 110, the voltage value of P% with respect to the voltage level of the TAA is outputted into the wave-form comparator circuit 608, as the slice setting 2.
The PW detector circuit 607 is constructed with, for example a voltage comparator circuit (comparator), a controlled current source, a capacitor and a one-round track integrator circuit (not shown in the figure), wherein the controlled current source is controlled by the comparator, so that the capacitor is charged up only for the time when the disc reproducing signal mentioned above exceeds the slice setting 1, to integrate the capacitor charging voltage for the period of one-turn or one-round of the track in the one-turn track integrator circuit, thereby detecting the integrated value (voltage) of the pulse widths.
The CPU 111 of the controller portion 110 measures the averaged pulse width PW 50 mentioned above, through conducting the dividing process upon the integrated value (voltage) of the pulse widths as the output of the PW detector circuit 607 by the charge current value of the controlled current source and the number of pulses of the disc reproducing signal for the period of one-turn of the track.
The wave-form comparator circuit 608 is constructed with, for example a voltage comparator circuit (comparator), and outputs a comparison result between the voltage value of the above-mentioned disc reproducing signal and the voltage value of the slice setting 2, as a detection signal to an error detection circuit 609. The error detection circuit 609 is constructed with gate circuits, wherein a window pulse is generated for detecting the peak position of the disc reproducing signal pulse, only for a predetermined set period upon the basis of a timing signal T corresponding to each bit of the test data which is sent from the test signal generator circuit 602 mentioned above, while detecting an error, such as the missing error and/or the spike error, etc., from the detection signal as the output of the wave-form comparator circuit 608 and the window pulse, thereby outputting a bit error signal Er to an error memory 610 in synchronism with the each bit of the timing signal T. The error detection circuit 609 also receives the control signal P from the CPU 111 of the controller portion 110, and is changed in the operation condition thereof depending upon the kinds or sorts of errors, so as to detect the each error, such as the missing error and/or the spike error, etc.
The error memory 610 changes the address thereof sequentially, while receiving the timing signal T generated by the test signal generator circuit 602, and also memorizes the error signal Er which is outputted by the error detection circuit 609 into the renewed address, as a defect data, xe2x80x9c1xe2x80x9d or xe2x80x9c0xe2x80x9d, sequentially. The CPU 111 reads the contents of the error memory 610 at the time point when the test is completed on all rounds of the magnetic disc 101 as the object to be tested, through a bus into a memory 112, so as to conduct the evaluation of the magnetic disc 101.
Though the above-mentioned is for the magnetic disc as the object to be tested, however when the object to be tested is a magnetic head, the evaluation on the R/W head 102 as the magnetic head is carried out, with using the magnetic disc which was acknowledged to be a good-qualified one or is known in the magnetic characteristics thereof, under the same construction.
Accordingly, with the testing apparatus of the magnetic recording medium or the magnetic head according to the conventional art, shown in the FIG. 10, by performing the circuit operation mentioned above onto the magnetic disc 101 as the object to be tested, it measures the TAA or the PW50, thereby to realizes the prametric test, or it measures the missing error or the spike error, thereby to realize the certify test. As the prior art relating to the present technology, for example, in Japanese Patent Laying-Open No. Hei 10-83501 (1998) is mentioned an outline of the conventional certifier.
However, with the testing apparatus of the magnetic recording medium or the magnetic head of analogue method, according to the conventional art, there is given no consideration on measuring restrictively the TAA shown in the FIG. 1, for example for detecting the value of amplitude of the disc reproducing signal, with using the envelope detector circuit, as was mentioned in the above, nor consideration of conducting the test with details and at high accuracy onto the magnetic disc, by detecting the pulse width or the value of amplitude, etc., for example, on an arbitrary number of discontinuous pulses of the disc reproducing signal, for measuring the TAA and the PW50 from the disc reproducing signal by treating the averaging process thereon with using the one-turn track integrator circuit.
Also, in the testing apparatus of the magnetic recording medium or the magnetic head with using the conventional analogue method, when the disc reproducing signal comes to be a high frequency wave, the response of the comparator in the TAA detector circuit, for example, is too late to the changing of an input, then the accuracy is deteriorated in detecting the TAA. In a case where the TAA is measured at the detecting accuracy being same to that of the conventional method, so as to meet with tendency of high frequency on the magnetic disc in future, for example, there is a necessity for the comparator , having a performance of gain 54 db/frequency bandwidth 2 GHz at the present, to be improved in IC process performance more than 8 GHz in the frequency bandwidth thereof, i.e., more than four (4) times lager than that, however it is difficult to realize it with the present IC process technology. Accordingly, with the conventional method, there is a possibility that the test of the magnetic disc or the magnetic head cannot be performed with high accuracy at the frequency where it is practiced actually, in particular for the tendency of high frequency of the magnetic disc apparatus in future, namely there is a problem that the test cannot be carried out at high speed/high accuracy, and that the magnetic disc or the magnetic head as the object to be tested is decreased down in the reliability thereof.
Also, in the testing apparatus of the magnetic recording medium or the magnetic head with using the conventional analogue method, there is a testing method to cope with the tendency of high frequency of the magnetic disc apparatus, in which the digital reproducing signal is observed on the wave-form with using a digital sampling oscilloscope, etc., however it has a problem that it is impossible to measure the disc reproducing signal, with observing the wave-form there of by means of the digital sampling oscilloscope, in particular for the write-in of an arbitrary and aperiodic test data. Also, even in a case of measuring the wave-form of the disc reproducing signal by means of the digital sampling oscilloscope, etc., with using a periodic test data, there is a problem that it is impossible to achieve the high speed in the testing time, then throughput in the testing process of the magnetic disc is decreased down, therefore the price of the magnetic disc cannot be lowered, in particular when conducting the test on recording/reproducing of the test data onto/from all the tracks of the magnetic disc.
An object according to the present invention is to provide a testing apparatus of the magnetic recording medium or the magnetic head, with which the test can be realized on the magnetic disc or the magnetic head, with details and at high accuracy.
Also other object according to the present invention is to provide a testing apparatus of the magnetic recording medium or the magnetic head, with which the test can be realized on the magnetic disc or the magnetic head, with details thereof and at accuracy being much higher.
Also, other object according to the present invention is to provide a testing apparatus of the magnetic recording medium or the magnetic head, with which the test can be realized at high speed, in the testing apparatus of the magnetic recording medium or the magnetic head.
Also, other object according to the present invention is to provide a testing apparatus of the magnetic recording medium or the magnetic head, with which measurement of the value of average amplitude (TAA) and the average pulse width PW50 of the reproducing test data can be realized at high speed.
According to the present invention, there is provided a testing apparatus of a magnetic recording medium or of a magnetic head, for conducting test on said magnetic recording medium or said magnetic head, through recording test data onto said magnetic recording medium by means of said magnetic head and reproducing said recorded test data by means of said magnetic head, so as to treat a predetermined process thereon, wherein:
said reproduced test data is converted into a digital value, and upon said converted digital data, a calculation process is conducted in relation to a magnetic characteristic of said magnetic recording medium from the converted digital value, thereby conducting the test on said magnetic recording medium or on said magnetic head.
Also, according to the present invention, there is provided a testing apparatus of a magnetic recording medium or of a magnetic head as defined in the above, wherein said calculation process is a statistic calculation process or a frequency analysis calculation process, in which a peak value of said reproduced test data or a threshold value time when exceeding or being below an arbitrary threshold value is measured with using said converted digital value, thereby to calculate out an average value or a dispersion value or a deviation value or a cumulative frequency about said peak value or said threshold value time.
Also, according to the present invention, there is provided a testing apparatus of a magnetic recording medium or of a magnetic head, for conducting test on said magnetic recording medium or said magnetic head, through recording test data onto said magnetic recording medium by means of said magnetic head and reproducing said recorded test data by means of said magnetic head, so as to treat a predetermined process thereon, comprising:
a conversion means for converting the reproduced test data into a digital value, a holding means for holding the digital value converted by said conversion means, and a data processing means for conducting a calculation process in relation to a magnetic characteristic of said magnetic recording medium from said digital value held by said holding means, thereby conducting the test on said magnetic recording medium or on said magnetic head.
Also, according to the present invention, there is provided a testing apparatus of a magnetic recording medium or of a magnetic head, for conducting test on said magnetic recording medium or said magnetic head, through recording test data onto said magnetic recording medium by means of said magnetic head and reproducing said recorded test data by means of said magnetic head, so as to treat a predetermined process thereon, comprising:
N number (N: an integer) of conversion means for converting the reproduced test data into digital values;
a sampling clock control means for operating said N number of said conversion means, at a predetermined sampling frequency for each one of said converter means;
N number of holding means for holding the digital values converted by said N number of the converter means; and
a data processing means for conducting a calculation process in relation to a magnetic characteristic of said magnetic recording medium from said digital values held by said N number of the holding means, thereby conducting the test on said magnetic recording medium or on said magnetic head.
Also, according to the present invention, there is provided a testing apparatus of a magnetic recording medium or of a magnetic head, for conducting test on said magnetic recording medium or said magnetic head, through recording test data onto said magnetic recording medium by means of said magnetic head and reproducing said recorded test data by means of said magnetic head, so as to treat a predetermined process thereon, comprising:
N number of conversion means for converting the reproduced test data into digital values;
a sampling clock control means for operating said N number of said conversion means, at a sampling frequency fADC for each one of said converter means;
N number of holding means for holding the digital values converted by said N number of the converter means;
a data processing means for conducting a calculation process in relation to a magnetic characteristic of said magnetic recording medium from said digital values held by said N number of the holding means; and
an analysis processing means for conducting determining process of said magnetic recording medium from an output of said data processing means, wherein N has a following relationship among M, being a ratio of a sampling frequency fs as a target with respect to a frequency fin of the reproduced test data, said frequency fin, and a sampling frequency fADC for operating said converter means,
xe2x80x83Nxe2x89xa7Mxc3x97fin/fADC
and is an integer.
Also, according to the present invention, there is provided a testing apparatus of a magnetic recording medium or of a magnetic head, for conducting test on said magnetic recording medium or said magnetic head, through recording test data onto said magnetic recording medium by means of a magnetic head and reproducing said recorded test data by means of said magnetic head, so as to treat a predetermined process thereon, comprising:
a rotation control means for operating a holding rotation means for holding said magnetic recording medium to rotate, by an output of a first oscillation means for oscillating at a desired frequency;
a recording means for recording said test data onto said magnetic recording medium, by the magnetic head which is positioned opposing to said magnetic recording medium on said holding rotation means;
a reproducing means for reproducing said test data which is recorded onto said magnetic recording medium by said magnetic head;
N number of conversion means for converting the reproduced test data into digital values;
a reproduction signal distributing means for distributing said reproduced test data into said N number of the converter means to supply;
a sampling clock distributing means for operating said N number of the converter means, at a sampling frequency fADC for each one of said converter means, by means of a clock signal based on a second oscillation means for oscillating at a desired frequency;
N number of holding means for holding the digital values converted by said N number of the converter means;
a data processing means for conducting a calculation process in relation to a magnetic characteristic of said magnetic recording medium from said digital values held by said N number of the holding means;
an analysis processing means for conducting determining process of said magnetic recording medium from an output of said data processing means; and
a controller means for bringing the oscillating frequencies of said first oscillation means and said second oscillation means and the sampling frequency for operating said converter means to be changeable, wherein N has a following relationship among M, being a ratio of a sampling frequency fs as an object with respect to a frequency fin of the reproduced testing data, said frequency fin, and a sampling frequency fADC for operating said converter means,
Nxe2x89xa7Mxc3x97fin/fADC
and is an integer.
Also, according to the present invention, there is provided a testing apparatus of a magnetic recording medium or of a magnetic head, for conducting test on said magnetic recording medium or said magnetic head, through recording test data onto said magnetic recording medium by means of said magnetic head and reproducing said recorded test data by means of said magnetic head, so as to treat a predetermined process thereon, comprising:
a rotation control means for operating a holding rotation means for holding said magnetic recording medium to rotate, by an output of a first oscillation means for oscillating at a desired frequency;
a mode and timing controller means for producing a write-in mode signal indicative of a start and an end of writing and a read-out mode signal indicative of a start and an end of reading, responding to a start signal and a stop signal, upon basis of an index signal indicative of a rotation number and an encode signal indicative of a rotating position from said rotation controller means;
a recording means for recording said test data onto said magnetic recording medium, by the magnetic head which is positioned opposing to said magnetic recording medium on said holding rotation means, upon basis of said write-in mode signal;
a reproducing means for reproducing said test data which is recorded onto said magnetic recording medium by said magnetic head, upon basis of said read-out mode signal;
N number of conversion means for converting the reproduced testing data into digital values;
a reproduction signal distributing means for distributing said reproduced test data into said N number of the converter means so supply;
a sampling clock distributing means for operating said N number of the converter means, at a sampling frequency fADC for each one of said converter means, by means of a clock signal based on a second oscillation means for oscillating at a desired frequency;
N number of holding means for holding the digital values converted by said N number of the converter means;
a data processing means for conducting a calculation process in relation to a magnetic characteristic of said magnetic recording medium from said digital values held by said N number of the holding means;
an analysis processing means for conducting determining process of said magnetic recording medium from an output of said data processing means; and
a controller means for bringing the oscillating frequencies of said first oscillation means and said second oscillation means and the sampling frequency for operating said converter means to be changeable, wherein N has a following relationship among M, being a ratio of a sampling frequency fs as an object with respect to a frequency fin of the reproduced testing data, said frequency fin, and a sampling frequency fADC for operating said converter means,
Nxe2x89xa7Mxc3x97fin/fADC
and is an integer.
Also, according to the present invention, there is provided a testing apparatus of a magnetic recording medium or of a magnetic head, for conducting test on said magnetic recording medium or said magnetic head, through recording test data onto said magnetic recording medium by means of said magnetic head and reproducing said recorded test data by means of said magnetic head, so as to treat a predetermined process thereon, comprising:
L (L: an integer being equal or greater than 2) number of reproducing means for reproducing said test data recorded onto said magnetic recording medium, as L number of separate signals, by means of L number of said magnetic heads which are positioned opposing to said magnetic recording medium;
N (N: an integer being equal or greater than 2) number of conversion means for converting the reproduced test data into digital values;
a reproduction signal distributing means for distributing said reproduced test data into said N number of the converter means to supply, by bringing into a desired connecting condition;
a sampling clock distributing means for operating said N number of the converter means, at a sampling frequency fADC for each one of said converter means;
N number of holding means for holding the digital values converted by said N number of the converter means; and
a data processing means for conducting a calculation process in relation to a magnetic characteristic of said magnetic recording medium from said digital values held by said N number of the holding means, thereby conducting the test on said magnetic recording medium or on said magnetic head.
Also, according to the present invention, there is provided a testing apparatus of a magnetic recording medium or of a magnetic head, for conducting test on said magnetic recording medium or said magnetic head, through recording test data onto said magnetic recording medium by means of said magnetic head and reproducing said recorded test data by means of said magnetic head, so as to treat a predetermined process thereon, wherein:
said reproduced testing data is converted into a digital value, and upon said converted digital data, a calculation process is conducted in relation to a magnetic characteristic of said magnetic recording medium from the converted digital value, thereby conducting the test on said magnetic recording medium, and said calculation process comprises:
a first frequency measuring means for selectively operating plural measuring means to measure, upon basis of said converted digital value;
a first histogram processing means for measuring and outputting an average amplitude value of a reproduced wave-form by means of a histogram process, upon basis of an output of said first frequency measuring means;
a coefficient means for multiplying a coefficient of xc2xd onto an output of said first histogram processing means;
a comparator means for comparing an output of said coefficient means and an output of a converter means, to output a comparison result;
a pulse counting means for operating to count a clock signal pulse oscillating at a desired frequency, only a period during when an output of said comparator means lies at a predetermined level;
a second frequency measuring means, being operative upon basis of change of an output of said comparator means, for selectively operating the plural measuring means to measure, upon basis of a pulse which is outputted by said pulse counting means; and
a second histogram processing means for measuring and outputting an average amplitude value of the reproduced wave-form by means of a histogram process upon basis of an output of said second frequency measuring means, wherein the average amplitude value and the average pulse width of said reproduced wave-form during a desired time period is measured, thereby conducting the test on said magnetic recording medium or on said magnetic head.
Also, according to the present invention, there is provided a testing apparatus of a magnetic recording medium or of a magnetic head, for conducting test on said magnetic recording medium or said magnetic head, through recording test data onto said magnetic recording medium by means of said magnetic head and reproducing said recorded test data by means of said magnetic head, so as to treat a predetermined process thereon, wherein:
said reproduced testing data is converted into a digital value, and upon said converted digital data, a calculation process is conducted in relation to a magnetic characteristic of said magnetic recording medium from the converted digital value, thereby conducting the test on said magnetic recording medium, and said calculation process comprises:
a first frequency value holding means for measuring frequency, by adding data written into an address of a first memory corresponding to said converted digital value with using a first adder circuit and writing it into the same address, upon basis of said converted digital value;
a first histogram processing means for measuring and outputting an average amplitude value of a reproduced wave-form by means of a histogram process, upon basis of an output of said first frequency measuring means;
a threshold holding means for holding a predetermined threshold data;
a comparator means for comparing an output of said threshold holding means and an output of said converter means, so as to output a comparison result therefrom;
a pulse counting means for operating to count a clock signal pulse at a desired frequency, only a period during when an output of said comparator means lies at a predetermined level;
a second frequency holding means for measuring frequency, by adding data written into an address of a second memory corresponding to said converted digital value, with using a second adder circuit and by writing it into the same address, upon basis of an output of said pulse counting means; and
a second histogram processing means for measuring and outputting a value of average amplitude of a reproduced wave-form, by means of a histogram calculation process, upon basis of an output of said first frequency measuring means, wherein the average amplitude value and the average pulse width of said reproduced wave-form during a desired time period is measured, thereby conducting the test on said magnetic recording medium or on said magnetic head.